Longevity combined with good health and functioning at the end of life is the goal of most individuals. Finding ways of promoting this condition is an important goal of the National Institute on Aging (NIA). Although research has been done on the correlates of long life and functional decline, we still know relatively little about why certain individuals live in excellent health into their 80's while others fail much sooner. In other words, how factors related to physiology and pathology affect longevity and healthy aging is not clear. It may be hypothesized that in older persons who escape diseases and disability, homeostatic mechanisms (integrity of anti-oxidant mechanisms, low level of oxidative damage to macromolecules, low inflammation, unimpaired autonomic reflexes, normal hormone levels etc.) should be relatively intact, with little accumulated damage. Understanding these mechanisms may open new opportunities of disability prevention.